This proposal describes a project which will attempt to transfer the receptor for the peptide hormone, thyrotropin-releasing hormone (TRH) from a TRH-responsive strain of rat pituitary tumor cells, GH3 cells, to a TRH non-responsive strain, GH12C1. The TRH non-responsive strain lacks TRH receptors. A major focus of this project will be to determine if the presence of TRH receptors in GH12C1 cells will confer biological responsiveness to TRH in these recipients. TRH receptors will be transferred using a polyethylene glycol (PEG) mediated procedure in which membrane fractions from GH3 cells will be fused to recipient cells. The transfer of TRH receptors to recipient cells will be assessed by assays which will measure the binding of (3H)-TRH to recipient cells. Biological responsiveness to TRH will be measured by examining growth hormone (GH) release and synthesis in control cells and the cells which have received TRH receptors, some of which will be untreated, and some will be exposed to TRH. The long term goals of this study are to determine the role of the cell membrane in peptide hormone-mediated responses and to help to elucidate the pathway of peptide hormone action, especially with regard to the regulation of gene expression.